Abstract: Electron paramagnetic resonance (EPR) is a powerful technique for the study of systems with paramagnetic centers, such as transition metals and organic radical ions, and is among the most important tools for studying transient radical pairs in photoexcited systems. Thus, progress in the understanding of redox processes and various complex reactions in all kinds of chemical and biochemical systems associated with paramagnetic intermediates has been strongly promoted by the application of in situ spectroelectrochemical techniques. Because of its high sensitivity to paramagnetic species, EPR can provide key information about radical species generated or consumed during electrochemical reactions. In this way, EPR complements electrochemical data from other techniques by directly identifying radical species, confirming reaction mechanisms, and revealing more subtle interactions, for example, between the radical and its environment. As such, EPR has not only provided a wealth of information to electrochemists, but EPR spectroscopists have also found that in situ electrochemical EPR is a feasible alternative to standard optical study of electrochemistry.

Currently, most studies of electron transfer reactions are carried out by chemically generating paramagnetic intermediates ex situ, followed by a transfer to the spectroscopic cell. In most cases, those paramagnetic intermediates are not long-lived and need an oxygen-free environment. In addition, chemical generation of these radical ion intermediates is not as accurate as electrochemical generation and can generate by-products as well. In my talk, I will discuss an easy, affordable and robust setup for in situ electrochemical EPR that was used to study and characterize radical ions and catalysts.